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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 289 records · Page 16
All sourcesNASA NTRSDOE OSTI
DOE OSTI2011

Comparison of Treatment Outcome Between Breast-Conservation Surgery With Radiation and Total Mastectomy Without Radiation in Patients With One to Three Positive Axillary Lymph Nodes

Purpose: To test the difference in treatment outcome between breast-conservation surgery with radiation and total mastectomy without radiation, to evaluate the benefits of adjuvant radiotherapy in patients with one to three positive axillary lymph nodes. Methods and Materials: Using the Severance Hospital Breast Cancer Registry, we divided the study population of T1, T2 and one to three axillary node-positive patients into two groups: breast-conservation surgery with radiation (BCS/RT) and total mastectomy without radiation (TM/no-RT). Data related to locoregional recurrence, distant recurrence, and death were collected, and survival rates were calculated. Results: The study population consisted of 125 patients treated with BCS/RT and 365 patients treated with TM/no-RT. With a median follow-up of 68.4 months, the 10-year locoregional recurrence-free survival rate with BCS/RT and TM/no-RT was 90.5% and 79.2%, respectively (p = 0.056). The 10-year distant recurrence-free survival rate was 78.8% for patients treated with BCS/RT vs. 68.0% for those treated with TM/no-RT (p = 0.012). The 10-years overall survival rate for patients treated with BCT/RT and TM/no-RT was 87.5% and 73.9%, respectively (p = 0.035). After multivariate analysis, patients treated with BCT/RT had better distant recurrence-free survival (hazard ratio [HR], 0.527; 95% confidence interval [CI], 0.297-0.934; p = 0.028), with improving locoregional recurrence-free survival (HR, 0.491; 95% CI, 0.231-1.041; p = 0.064) and overall survival trend (HR, 0.544; 95% CI, 0.277-1.067; p = 0.076). Conclusions: This study provides additional evidence that adjuvant radiation substantially reduces local recurrence, distant recurrence, and mortality for patients with one to three involved nodes.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2015

Expert Radiation Oncologist Interpretations of Involved-Site Radiation Therapy Guidelines in the Management of Hodgkin Lymphoma

Purpose: Recently, involved-site radiation therapy (ISRT) guidelines have been developed and published to replace the previous concept of involved-field radiation therapy for patients with lymphoma. However, these ISRT guidelines may be interpreted in different ways, posing difficulties for prospective clinical trials. This study reports survey results regarding interpretation of the ISRT guidelines. Methods and Materials: Forty-four expert lymphoma radiation oncologists were asked to participate in a survey that included 7 different cases associated with 9 questions. The questions pertained to ISRT contouring and asked respondents to choose between 2 different answers (no “correct” answer) and a third write-in option allowed. Results: Fifty-two percent of those surveyed responded to the questionnaire. Among those who responded, 72% have practiced for >10 years, 46% have treated >20 Hodgkin lymphoma cases annually, and 100% were familiar with the ISRT concept. Among the 9 questions associated with the 7 cases, 3 had concordance among the expert radiation oncologists of greater than 70%. Six of the questions had less than 70% concordance (range, 56%-67%). Conclusions: Even among expert radiation oncologists, interpretation of ISRT guidelines is variable. Further guidance for ISRT field design will be needed to reduce variability among practicing physicians.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2015

Imaging Changes in Pediatric Intracranial Ependymoma Patients Treated With Proton Beam Radiation Therapy Compared to Intensity Modulated Radiation Therapy

Purpose: The clinical significance of magnetic resonance imaging (MRI) changes after radiation therapy (RT) in children with ependymoma is not well defined. We compared imaging changes following proton beam radiation therapy (PBRT) to those after photon-based intensity modulated RT (IMRT). Methods and Materials: Seventy-two patients with nonmetastatic intracranial ependymoma who received postoperative RT (37 PBRT, 35 IMRT) were analyzed retrospectively. MRI images were reviewed by 2 neuroradiologists. Results: Sixteen PBRT patients (43%) developed postradiation MRI changes at 3.8 months (median) with resolution by 6.1 months. Six IMRT patients (17%) developed changes at 5.3 months (median) with 8.3 months to resolution. Mean age at radiation was 4.4 and 6.9 years for PBRT and IMRT, respectively (P=.06). Age at diagnosis (>3 years) and time of radiation (≥3 years) was associated with fewer imaging changes on univariate analysis (odds ratio [OR]: 0.35, P=.048; OR: 0.36, P=.05). PBRT (compared to IMRT) was associated with more frequent imaging changes, both on univariate (OR: 3.68, P=.019) and multivariate (OR: 3.89, P=.024) analyses. Seven (3 IMRT, 4 PBRT) of 22 patients with changes had symptoms requiring intervention. Most patients were treated with steroids; some PBRT patients also received bevacizumab and hyperbaric oxygen therapy. None of the IMRT patients had lasting deficits, but 2 patients died from recurrent disease. Three PBRT patients had persistent neurological deficits, and 1 child died secondarily to complications from radiation necrosis. Conclusions: Postradiation MRI changes are more common with PBRT and in patients less than 3 years of age at diagnosis and treatment. It is difficult to predict causes for development of imaging changes that progress to clinical significance. These changes are usually self-limiting, but some require medical intervention, especially those involving the brainstem.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2016

Image Guided Radiation Therapy (IGRT) Practice Patterns and IGRT's Impact on Workflow and Treatment Planning: Results From a National Survey of American Society for Radiation Oncology Members

Purpose: To survey image guided radiation therapy (IGRT) practice patterns, as well as IGRT's impact on clinical workflow and planning treatment volumes (PTVs). Methods and Materials: A sample of 5979 treatment site–specific surveys was e-mailed to the membership of the American Society for Radiation Oncology (ASTRO), with questions pertaining to IGRT modality/frequency, PTV expansions, method of image verification, and perceived utility/value of IGRT. On-line image verification was defined as images obtained and reviewed by the physician before treatment. Off-line image verification was defined as images obtained before treatment and then reviewed by the physician before the next treatment. Results: Of 601 evaluable responses, 95% reported IGRT capabilities other than portal imaging. The majority (92%) used volumetric imaging (cone-beam CT [CBCT] or megavoltage CT), with volumetric imaging being the most commonly used modality for all sites except breast. The majority of respondents obtained daily CBCTs for head and neck intensity modulated radiation therapy (IMRT), lung 3-dimensional conformal radiation therapy or IMRT, anus or pelvis IMRT, prostate IMRT, and prostatic fossa IMRT. For all sites, on-line image verification was most frequently performed during the first few fractions only. No association was seen between IGRT frequency or CBCT utilization and clinical treatment volume to PTV expansions. Of the 208 academic radiation oncologists who reported working with residents, only 41% reported trainee involvement in IGRT verification processes. Conclusion: Consensus guidelines, further evidence-based approaches for PTV margin selection, and greater resident involvement are needed for standardized use of IGRT practices.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2016

Better Efficacy of Synchrotron Spatially Microfractionated Radiation Therapy Than Uniform Radiation Therapy on Glioma

Purpose: Synchrotron microbeam radiation therapy (MRT) is based on the spatial fractionation of the incident, highly focused synchrotron beam into arrays of parallel microbeams, typically a few tens of microns wide and depositing several hundred grays. This irradiation modality was shown to have a high therapeutic impact on tumors, especially in intracranial locations. However, mechanisms responsible for such a property are not fully understood. Methods and Materials: Thanks to recent progress in dosimetry, we compared the effect of MRT and synchrotron broad beam (BB) radiation therapy delivered at comparable doses (equivalent to MRT valley dose) on tumor growth control and on classical radiobiological functions by histologic evaluation and/or transcriptomic analysis. Results: MRT significantly improved survival of rats bearing 9L intracranial glioma compared with BB radiation therapy delivered at a comparable dose (P<.001); the efficacy of MRT and BB radiation therapy was similar when the MRT dose was half that of BB. The greater efficacy of MRT was not correlated with a difference in cell proliferation (Mki67 and proliferating cell nuclear antigen) or in transcriptomic stimulation of angiogenesis (vascular endothelial growth factor A or tyrosine kinase with immunoglobulin-like and epidermal growth factor-like domains 2) but was correlated with a higher cell death rate (factor for apoptosis signals) and higher recruitment of macrophages (tyrosine kinase with immunoglobulin-like and epidermal growth factor-like domains 1 and CD68 transcripts) a few days after MRT. Conclusions: These results show the superiority of MRT over BB radiation therapy when applied at comparable doses, suggesting that spatial fractionation is responsible for a specific and particularly efficient tissue response. The higher induction of cell death and immune cell activation in brain tumors treated by MRT may be involved in such responses.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2018

Synergistically Enhancing the Therapeutic Effect of Radiation Therapy with Radiation Activatable and Reactive Oxygen Species-Releasing Nanostructures

Nanoparticle-based radio-sensitizers can amplify the effects of radiation therapy on tumor tissue even at relatively low concentrations while reducing the potential side effects to healthy surrounding tissues. In this study, we investigated a hybrid anisotropic nanostructure, composed of gold (Au) and titanium dioxide TiO 2 , as a radio-sensitizer for radiation therapy of triple negative breast cancer (TNBC). In contrast to other gold-based radio sensitizers, dumbbell-like Au-TiO 2 nanoparticles (DATs) show a synergistic therapeutic effect on radiation therapy, mainly because of strong asymmetric electric coupling between the high atomic number metals and dielectric oxides at their interfaces. The generation of secondary electrons and reactive oxygen species (ROS) from DATs triggered by X-ray irradiation can significantly enhance the radiation effect. After endocytosed by cancer cells, DATs can generate a large amount of ROS under X-ray irradiation, eventually inducing cancer cell apoptosis. Significant tumor growth suppression and overall improvement in survival rate in a TNBC tumor model have been successfully demonstrated under DATs uptake for a radio-sensitized radiation therapy.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2024

Silicon ion radiation as a viable surrogate for emulating neutron radiation damage in silicates

Abstract Nuclear power plants are aging around the world, and a precise assessment of irradiation damage in their components is needed. One key component, concrete, and specifically the silicates in its aggregates, can undergo significant expansion upon neutron radiation, which can lead to cracking and, ultimately, structural failure. However, assessing and predicting the extent of damage via neutron radiation is challenging due to reasons such as residual radioactivity and, most importantly, the high time involved. Here, we evaluate whether ion radiation can be a viable surrogate. Specifically, by employing Si 2+ ion radiations and a comprehensive multi-modal imaging protocol, we report mineral-specific responses for key silicates such as quartz, albite, anorthite, and microcline. We find that 10 MeV Si 2+ ions result in mineral expansions that are remarkably comparable to neutron radiation equivalent expansions (R 2 = 0.86, RMSE = 1.29%), opening up pathways towards rapid assessment of silicates subject to irradiation.

36 MATERIALS SCIENCE↗
DOE OSTI2011

Radiation-induced mechanical property changes in filled rubber

In a recent paper we exposed a filled elastomer to controlled radiation dosages and explored changes in its cross-link density and molecular weight distribution between network junctions [A. Maiti et al., Phys. Rev. E 83, 031802 (2011)]. Here we report mechanical response measurements when the material is exposed to radiation while being under finite nonzero strain. We observe interesting hysteretic behavior and material softening representative of the Mullins effect, and materials hardening due to radiation. The net magnitude of the elastic modulus depends upon the radiation dosage, strain level, and strain-cycling history of the material. Using the framework of Tobolsky's two-stage independent network theory we develop a model that can quantitatively interpret the observed elastic modulus and its radiation and strain dependence.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Outstanding radiation resistance of tungsten-based high-entropy alloys

A body-centered cubic W-based refractory high entropy alloy with outstanding radiation resistance has been developed. The alloy was grown as thin films showing a bimodal grain size distribution in the nanocrystalline and ultrafine regimes and a unique 4-nm lamella-like structure revealed by atom probe tomography (APT). Transmission electron microscopy (TEM) and x-ray diffraction show certain black spots appearing after thermal annealing at elevated temperatures. TEM and APT analysis correlated the black spots with second-phase particles rich in Cr and V. No sign of irradiation-created dislocation loops, even after 8 dpa, was observed. Furthermore, nanomechanical testing shows a large hardness of 14 GPa in the as-deposited samples, with near negligible irradiation hardening. Theoretical modeling combining ab initio and Monte Carlo techniques predicts the formation of Cr- and V-rich second-phase particles and points at equal mobilities of point defects as the origin of the exceptional radiation tolerance.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Enhancing Cloud Radiative Processes and Radiation Efficiency in the Advanced Research Weather Research and Forecasting (WRF) Model

The objective of this research has been to evaluate and implement enhancements to the computational performance of the RRTMG radiative transfer option in the Advanced Research version of the Weather Research and Forecasting (WRF) model. Efficiency is as essential as accuracy for effective numerical weather prediction, and radiative transfer is a relatively time-consuming component of dynamical models, taking up to 30-50 percent of the total model simulation time. To address this concern, this research has implemented and tested a version of RRTMG that utilizes graphics processing unit (GPU) technology (hereinafter RRTMGPU) to greatly improve its computational performance; thereby permitting either more frequent simulation of radiative effects or other model enhancements. During the early stages of this project the development of RRTMGPU was completed at AER under separate NASA funding to accelerate the code for use in the Goddard Space Flight Center (GSFC) Goddard Earth Observing System GEOS-5 global model. It should be noted that this final report describes results related to the funded portion of the originally proposed work concerning the acceleration of RRTMG with GPUs in WRF. As a k-distribution model, RRTMG is especially well suited to this modification due to its relatively large internal pseudo-spectral (g-point) dimension that, when combined with the horizontal grid vector in the dynamical model, can take great advantage of the GPU capability. Thorough testing under several model configurations has been performed to ensure that RRTMGPU improves WRF model run time while having no significant impact on calculated radiative fluxes and heating rates or on dynamical model fields relative to the RRTMG radiation. The RRTMGPU codes have been provided to NCAR for possible application to the next public release of the WRF forecast model.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2018

DOE ASR Final Report on “Use of ARM Observations to Investigate the Role of Tropical Radiative Processes and Cloud Radiative Effects in Climate Simulations”

The overall objective of this ASR funded project is to investigate the role of cloud radiative effects, especially those associated with tropical thin cirrus clouds in the tropical tropopause layer, by analyzing the ARM observations combined with numerical models. In particular, we have processed and analyzed the observations from the Raman lidar at the ARM SGP and TWP sites. In the tenure of the project (8/15/2013 – 8/14/2016 and with a no-cost extension to 8/14/2017), we have been concentrating on (i) developing an automated feature detection scheme of clouds and aerosols for the ARM Raman lidar; (ii) developing an automated retrieval of cloud and aerosol extinctions for the ARM Raman lidar; (iii) investigating cloud radiative effects based on the observations on the simulated temperatures in the tropical tropopause layer using a radiative-convective model; and (iv) examining the effect of changes of atmospheric composition on the tropical lower-stratospheric temperatures. In addition, we have examined the biases in the CALIPSO-inferred aerosol direct radiative effects using ground-based Raman lidars at the ARM SGP and TWP sites, and estimated the impact of lidar detection sensitivity on assessing global aerosol direct radiative effects. We have also investigated the diurnal cycle of clouds and precipitation at the ARM site using the cloud radar observations along with simulations from the multiscale modeling framework. The main results of our research efforts are reported in the six referred journal publications that acknowledge the DOE Grant DE-SC0010557.

47 OTHER INSTRUMENTATION↗
DOE OSTI2020

Development of Gamma Background Radiation Digital Twin with Machine Learning Algorithms: Application of Unsupervised Machine Learning to Detection of Anomalies and Nuisances in Gamma Background Radiation Environmental Screening Data

Environmental screening of gamma radiation consists of detecting weak nuisance and anomaly signal in the presence of strong and highly varying background. In a typical scenario, a mobile detector-spectrometer continuously measures gamma radiation spectra in short, e.g., one-second, signal acquisition intervals. The measurement data is a 2D matrix, where one dimension is gamma ray energy, and the other dimension is the number of measurements or total time. In principle, gamma radiation sources can be detected and identified from the measured data by their unique spectral lines. Detecting sources from data measured in a search scenario is difficult due to the highly varying background because of naturally occurring radioactive material (NORM), and low signal-to-noise ratio (S/N) of spectral signal measured during one-second acquisition intervals. The objective of this work is to explore unsupervised machine learning (ML) algorithms for development of a digital twin of gamma radiation background, and for detection and identification of weak nuisances and anomalies events in the presence of highly fluctuating background. In one segment of work, we developed a gamma background estimation model using a Longshort term memory (LSTM) network for one-step CPS time series prediction. The LSTM model was validated with two data sets of measurements from two independent NaI detectors positioned on a mobile platform. The data sets contained background radiation only and no orphan isotope sources. The LSTM model was constructed and tested using data from one of the detectors. Performance of the LSTM model was validate through one-step prediction of CPS time series of another NaI detector without re-training. This approach allows to create a digital twin for nuclear background estimation. Using LSTM, it could be possible to detect a source through subtraction of the estimated counts from the measured background. In another segment of work, we investigated detection of gamma emitting sources in the presence of complex background using unsupervised machine learning. Spectral lines of isotopes are difficult to observe in one-second measurements. Averaging over the entire measurement campaign data set reveals spectral lines of most common background isotopes. Spectral lines of orphan sources, which might appear only in a few measurements during the campaign, will be washed out if averaging is performed over the entire measurement data set. The approach we have explored consists of extracting one-second measurements containing weak spectral features through data clustering. Averaging one-second spectra in a cluster should reveal the presence of anomaly sources. We created two ML models using K-means clustering and Neural Network Self-organizing Map (SOM). Performance of these ML models was benchmarked using search data. One data set contained 137 Cs source, and another dataset contained 131 I source.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2020

Impact of biomass burning aerosols on radiation, clouds, and precipitation over the Amazon: relative importance of aerosol–cloud and aerosol–radiation interactions

Biomass burning (BB) aerosols can influence regional and global climate through interactions with radiation, clouds, and precipitation. Here, we investigate the impact of BB aerosols on the energy balance and hydrological cycle over the Amazon Basin during the dry season. We performed simulations with a fully coupled meteorology–chemistry model, the Weather Research and Forecasting model coupled with Chemistry (WRF-Chem), for a range of different BB emission scenarios to explore and characterize nonlinear effects and individual contributions from aerosol–radiation interactions (ARIs) and aerosol–cloud interactions (ACIs). The ARIs of BB aerosols tend to suppress low-level liquid clouds by local warming and increased evaporation and to facilitate the formation of high-level ice clouds by enhancing updrafts and condensation at high altitudes. In contrast, the ACIs of BB aerosol particles tend to enhance the formation and lifetime of low-level liquid clouds by providing more cloud condensation nuclei (CCN) and to suppress the formation of high-level ice clouds by reducing updrafts and condensable water vapor at high altitudes (>8 km). For scenarios representing the lower and upper limits of BB emission estimates for recent years (2002–2016), we obtained total regional BB aerosol radiative forcings of –0.2 and 1.5 W m –2 , respectively, showing that the influence of BB aerosols on the regional energy balance can range from modest cooling to strong warming. We find that ACIs dominate at low BB emission rates and low aerosol optical depth (AOD), leading to an increased cloud liquid water path (LWP) and negative radiative forcing, whereas ARIs dominate at high BB emission rates and high AOD, leading to a reduction of LWP and positive radiative forcing. In all scenarios, BB aerosols led to a decrease in the frequency of occurrence and rate of precipitation, caused primarily by ACI effects at low aerosol loading and by ARI effects at high aerosol loading. The dependence of precipitation reduction on BB aerosol loading is greater in a strong convective regime than under weakly convective conditions. Overall, our results show that ACIs tend to saturate at high aerosol loading, whereas the strength of ARIs continues to increase and plays a more important role in highly polluted episodes and regions. This should hold not only for BB aerosols over the Amazon, but also for other light-absorbing aerosols such as fossil fuel combustion aerosols in industrialized and densely populated areas. The importance of ARIs at high aerosol loading highlights the need for accurately characterizing aerosol optical properties in the investigation of aerosol effects on clouds, precipitation, and climate.

54 ENVIRONMENTAL SCIENCES↗
NASA NTRS1976

Results of a comprehensive atmospheric aerosol-radiation experiment in the southwestern United States. I - Size distribution, extinction optical depth and vertical profiles of aerosols suspended in the atmosphere. II - Radiation flux measurements and

Results are reported for a field test that was aimed at acquiring a sufficient set of measurements of aerosol properties required as input for radiative-transfer calculations relevant to the earth's radiation balance. These measurements include aerosol extinction and size distributions, vertical profiles of aerosols, and radiation fluxes. Physically consistent, vertically inhomogeneous models of the aerosol characteristics of a turbid atmosphere over a desert and an agricultural region are constructed by using direct and indirect sampling techniques. These results are applied for a theoretical interpretation of airborne radiation-flux measurements. The absorption term of the complex refractive index of aerosols is estimated, a regional variation in the refractive index is noted, and the magnitude of solar-radiation absorption by aerosols and atmospheric molecules is determined.

Deluisi, J. J.↗
NASA NTRS1979

Studies of radiative transfer in the earth's atmosphere with emphasis on the influence of the radiation budget in the joint institute for advancement of flight sciences at the NASA-Langley Research Center

Earth and solar radiation budget measurements were examined. Sensor calibration and measurement accuracy were emphasized. Past works on the earth's radiation field that must be used in reducing observations of the radiation field were reviewed. Using a finite difference radiative transfer algorithm, models of the angular and spectral dependence of the earth's radiation field were developed.

Source record↗
NASA NTRS1987

Nimbus 7 earth radiation budget wide field of view climate data set improvement. II - Deconvolution of earth radiation budget products and consideration of 1982-1983 El Nino event

A deconvolution technique is employed that permits recovery of daily averaged earth radiation budget (ERB) parameters at the top of the atmosphere from a set of the Nimbus 7 ERB wide field of view (WFOV) measurements. Improvements in both the spatial resolution of the resultant fields and in the fidelity of the time averages is obtained. The algorithm is evaluated on a set of months during the period 1980-1983. The albedo, outgoing long-wave radiation, and net radiation parameters are analyzed. The amplitude and phase of the quasi-stationary patterns that appear in the spatially deconvolved fields describe the radiation budget components for 'normal' as well as the El Nino/Southern Oscillation (ENSO) episode years. They delineate the seasonal development of large-scale features inherent in the earth's radiation budget as well as the natural variability of interannual differences. These features are underscored by the powerful emergence of the 1982-1983 ENSO event in the fields displayed. The conclusion is that with this type of resolution enhancement, WFOV radiometers provide a useful tool for the observation of the contemporary climate and its variability.

Ardanuy, Phillip E.↗
NASA NTRS1989

Radiative forcing of the Venus mesosphere. II - Thermal fluxes, cooling rates, and radiative equilibrium temperatures

A radiative heat-transfer model is presently used to ascertain the way in which radiative forcing contributes to the up to 20 K higher temperature of the Venus polar regions, by comparison with the tropics, in the 60-100 km mesospheric levels. Model global-mean radiative equilibrium temperatures for 55-100 km are compared with observations to show how each opacity source contributes to the thermal structure. The results obtained from latitude-dependent radiative equilibrium experiments indicate that meridional variations in radiative forcing obliterate observed mesospheric temperature gradients and yield polar temperatures up to 40 K cooler than the tropics.

Crisp, David↗